Future generation aircraft (including helicopters) now in planning and/or development phases (as well as many present generation aircraft) are complex systems comprised of a large number of interrelated, complex subsystems such as the airframe, powerplant, main and tail rotor assemblies, flight controls, avionics, navigation equipment, armament, etc. Such subsystems generate significant amounts of status data, much of which must be frequently monitored by the pilot and/or co-pilot for the safe and/or efficient operation and/or pilotage of the aircraft. A considerable portion of the pilot workload in these future generation aircraft will be devoted to monitoring the status of the aircraft subsystems during flight operations via reference to generated status data.
Of particular concern to pilots is the operation of an aircraft within the defined flight envelope thereof such that aircraft subsystems are operated within the normal operating ranges established for such subsystems. Such normal operating ranges are based upon engineering criteria that ensure that such subsystems are not subjected to inadvertent dynamic stresses that may degrade the capability of the subsystem and preclude such subsystem from operating for specified life intervals (established time periods between inspections, maintenance, and/or replacement). Operation of such subsystems in exceedance of the established normal operating ranges may adversely impact the structural and/or functional integrity of such subsystems and may degrade the specified life intervals thereof. This can result in unnecessary aircraft downtime and cost for unscheduled subsystem post-flight inspections, maintenance, and/or replacements.
Conversely, however, flight conditions arise wherein the pilot must be able to utilize the maximum performance capability of the aircraft as provided through its various subsystems. Typically, aircraft subsystems are overdesigned (built-in safety margins) so that such subsystems may be operated at the upper limit of established normal operating ranges indefinitely without adversely affecting the specified life intervals of such subsystems. In addition, most subsystems have been overdesigned to such a degree that such subsystems may be operated in exceedance of the upper limit of the established normal operating ranges for a limited period of time, i.e., a time critical exceedance condition, without adversely impacting the specified life intervals thereof.
The established normal operating ranges, the upper limits of such operating ranges, and acceptable exceedance conditions beyond the established normal operating ranges (permissible exceedance ranges, predetermined exceedance time limits), are generally defined in the operator's manuals of complex aircraft. In addition, such subsystem information may be incorporated in the pilot's status displays for such subsystems (see, e.g., FIGS. 3 and 4 of the drawings and the accompanying description thereof hereinbelow). However, while such information regarding the exceedance of an established normal operating range for any specific subsystem is generally available to the pilot (either as personal knowledge or as incorporated in a status display), the burden is upon the pilot to continually monitor the status of numerous subsystems so as to be promptly aware of the exceedance of an established operating range. Moreover, a pilot must generally mentally track predetermined exceedance time limits for subsystems operating in time critical exceedance conditions. The pilot workload imposed by these conditions may be exacerbated if a subsystem has more than one defined time critical exceedance condition or if priorities must be established when more than one subsystem exceeds its established normal operating range.
Mission requirements for future generation aircraft may involve a greater percentage of high pilot workload operations such as nap-of-the-earth (NOE), adverse weather, and/or night flying. Such high pilot workload flight operations require the pilot to maintain a continual spatial awareness of aircraft orientation and/or location with respect to the external world and a situational awareness of objects of interest in the external world vis-a-vis the aircraft in addition to continual monitoring of the status of aircraft subsystems. Such high pilot workload operations may reduce the probability that a pilot will be promptly aware that operation of a specific subsystem has exceeded an established normal operating range. In addition, such high pilot workload operations adversely affect the pilot's ability to mentally track predetermined exceedance time limits for subsystems operating in time critical exceedance conditions. As a corollary of Murphy's Law, there is a high probability that flight conditions where the pilot must be able to utilize the maximum performance capability of the aircraft with respect to specific subsystems will occur during high pilot workload operations such that the pilot's ability to monitor and/or respond to time critical exceedance events is impaired.
A need exists for a cuing system that provides the pilot with a visual cue when a particular subsystem is operated so as to exceed its established normal operating range and operate in a time critical exceedance condition. A need exists to provide a visual cue that provides a time varying indication of the relative length of time wherein the particular subsystem has operated within the time critical exceedance condition. To effectuate prudent and efficient operation of such particular subsystem, the cuing system should also provide an indication of the appropriate recovery procedure to return the particular subsystem to operation within its established normal operating range. Furthermore, the visual cue generated by such cuing system should be cognitively connected to the particular subsystem and/or to the symbolic image or display representing the specific generated status data provided for monitoring the operation of the particular subsystem to facilitate pilot recognition of a particular time critical exceedance event.